There are many different types of circulating water systems. Three basic types are water cooling towers which are open systems, boilers which are closed systems, and chilled water systems which are also closed. More recently, cross-over cooling water systems, where both the tower water and the chilled water are combined for a period, are being employed.
If ultrahigh purity water were available in ample supply there would be little reason to chemically treat any of the water added to these systems. In actuality, however, highly pure water is rarely available. Therefore, operators of water systems must resort to chemical treatment to prevent damage to the water system which can be caused by the impurities contained in water.
There are literally dozens of treatment compositions that are currently added to these systems. The selection of the particular treatment agent depends on the type of water added, the particular water system employed, and operational conditions. Some of the types of treatment compositions added include dispersants, descalants, scale inhibitors, algacides, biocides, corrosion inhibitors, oxygen scavengers and pH modifiers. In each category of composition there are also a number of different particular compositions which can be used to accomplish the desired result. For example, phosphonates are typically used as anti-scaling agents and corrosion inhibitors. Chelating agents such as ethylenediamine tetraacetic acid and nitrilotriacetic acid are also anti-scaling agents. Corrosion inhibitors also include aromatic azoles, alkaline earth metal molybdates and so on.
Water systems are treated by adding the selected desired treatment agents separately or more likely a combination of treatment agents is dispensed into the water in the water system. Combinations for example could include corrosion inhibitors in combination with descalants and biocides for a water cooling tower. A boiler treatment composition may for example include an anti-scalant, corrosion inhibitors and oxygen scavenger.
Whether the treatment compositions are added separately or as a mixture it is necessary to determine the concentration level of the treatment agent or agents in the water system. Typically this has been done by simply taking a sample of the water in the system and performing a series of chemical analysis such as pH and various titrations to determine the concentration of the chemicals added.
One chemical that has been added in the past has been tannins and a similar composition lignins. These are anionic compositions which have been used in the past as dispersants. They are no longer the preferred dispersants since certain water soluble polymers have been developed which by far surpass the dispersing activities of these chemicals. However, these chemicals did have one incidental advantage in that they had a color and could be visually detected within a water system. Thus the boiler operator could visually detect the concentration of tannin or lignin in the system. When used they were added separately to the system. Therefore they did not provide any indication of the concentration of any other component.
Because tannins and lignins are anionic they cannot be added to a mixture which includes cationic treatment agents such as other dispersants and the like which can be cationic. In concentrated solutions, the tannins and lignins would precipitate out of solution and be totally ineffective.
Accordingly, to determine the concentration of the treatment agents in a water system one must perform complex titrations and other tests. This is inefficient and can result in ineffective treatment or a waste of treatment agents.